support for callbacks on native-proto events
support for callbacks on native-proto events

i.e., STATUS_CHANGE, TOPOLOGY_CHANGE

diezguerra/cassandra-dbapi2,CanWeStudio/cassandra-dbapi2,iGivefirst/cassandra-dbapi2,EnigmaCurry/cassandra-dbapi2,josh-mckenzie/cassandra-dbapi2,pandu-rao/cassandra-dbapi2,mshuler/cassandra-dbapi2,stanhu/cassandra-dbapi2,flowroute/cassandra-dbapi2,iflatness/cql,maraca/cassandra-dbapi2